The invention relates to an improved disk brake pad incorporated in a disk brake apparatus used to brake a vehicle such as an automobile and an improved disk brake apparatus. Specifically, the invention aims at realizing a structure which can prevent the generation of abnormal sounds called brake squeals and also can effectively prevent the occurrence of clonk sounds (click sounds).
In a disk brake apparatus used to brake a vehicle, a pair of pads are disposed to sandwich between them a rotor rotatable together with wheels and, in braking, the two pads are pressed against the two side surfaces of the rotor. The basic structure of such disk brake apparatus includes two kinds of structures of a floating type and an opposed piston type. FIGS. 15 to 19 show, of these two kinds of disk brake apparatuses, an example of the conventional structure of a floating caliper type of disk brake apparatus disclosed in the patent document 1.
Here, in the present specification and claims, “axial direction”, “circumferential direction” and “radial direction” respectively mean the axial direction, circumferential direction and radial direction of the rotor unless otherwise stated in a state where a disk brake pad is assembled to a disk brake apparatus. Further, “entrance side” means the side of the caliper where the rotor rotating together with the wheels enters the caliper, while “escape side” means the side where the rotor comes off from the caliper.
In the disk brake apparatus of the conventional structure, a caliper 3 is supported shiftably in the axial direction on a support 2 fixed to a vehicle body while it is opposed to the inner side surface of a rotor 1. Thus, on the circumferential-direction two end portions of (the inner side portions 6 to be discussed later) of the support 2, there are provided slide pins 4a, 4b while they project inwardly. The slide pins 4a, 4b are respectively engaged with a pair of support arm portions 5 projectingly formed in the circumferential-direction two sides of the caliper 3, thereby supporting the caliper 3 shiftably in the axial direction on the support 2.
The support 2 is constituted of an inner side portion 6 disposed on the inner side of the rotor 1 and an outer side portion 7 on the outer side, while they are connected together in their respective circumferential-direction two ends by a pair of connecting arm portions 8a, 8b disposed to straddle over the rotor 1. To the circumferential-direction two ends of the inner side and outer side portions 6 and 7, there are fixed pad pins 9a, 9b, 10a and 10b while they extend in the axial direction. On the other hand, inner side and outer side pads 11a, 11b are respectively constituted of linings 12, 12 and back plates 13, 13 attached to and supported on the backs of the linings 12, 12 and, in the circumferential-direction two ends of the back plates 13, 13, there are formed through holes 14a, 14b respectively. The pad pins 9a, 9b (10a, 10b) supported by the support 2 are loosely engaged into the respective through holes 14a, 14b. With this structure, the two pads 11a, 11b are supported movably in the axial direction on the support 2.
The caliper 3 includes a cylinder portion 15 and a caliper pawl 16 while they sandwich the two pads 11a, 11b from the axial-direction two sides. The cylinder portion 15 incorporates therein a piston 17 for pressing the inner-side pad 11a toward the rotor 1.
When enforcing braking, pressure oil is fed into the cylinder portion 15 to allow the piston 17 to press the inner-side pad 11a against the inner side surface of the rotor 1. Then, as the reaction of this pressing force, the caliper 3 is shifted in the axial direction (toward the inner side), whereby the caliper pawl 16 presses the outer-side pad 11b against the outer side surface of the rotor 1. Thus, the rotor 1 is strongly held from both sides to thereby enforce braking.
In the disk brake apparatus of the above conventional structure, using the paired pad pins 9a, 9b, 10a, 10b respectively disposed in the axial direction, the two pads 11a, 11b are supported movably in the axial direction on the support 2. Thus, the shapes of the two pads 11a, 11 b and support 2 can be formed symmetric with respect to their respective circumferential directions. This has an advantage in reducing the manufacturing cost of the disk brake apparatus.
However, in the disk brake apparatus of the above conventional structure, in braking, an abnormal sound called a clonk sound (click sound) is easy to occur. The reason for this is described with reference to FIG. 19.
When the rotation direction of the rotor 1 in the forward run of a vehicle is counterclockwise in FIG. 19, in braking, a brake tangential force F1 going toward the other side (in FIG. 19, the left side, escape side) in the circumferential direction is applied to the friction surface center A point of the lining 12 constituting the pad 11a. And, the pad 11a is slightly moved toward the other side in the circumferential direction, whereby the through hole 14a of the circumferential-direction one end portion (entrance side end portion) of the back plate 13 is engaged with the pad pin 9a fixed to the circumferential-direction one side portion of the support 2 to thereby support the brake tangential force F1 (that is, a so called pull anchor structure is established). Here, since the engagement portion between the through hole 14a and pad pin 9a is situated more inward in the radial direction than the action line of the brake tangential force F1, in the forward-run braking, to the pad 11a, there is applied the moment M1 based on the brake tangential force F1 to rotate the pad 11a counterclockwise.
On the other hand, in the vehicle backward-run braking, a brake tangential force F2 going toward the circumferential-direction one side (in FIG. 19, right side) is applied to the friction surface center A point. The pad 11a is slightly moved toward the circumferential-direction one side (entrance side) and the through hole 14b of the circumferential-direction other end portion of the back plate 13 is engaged with the pad pin 9b fixed to the circumferential-direction other end portion of the support 2 to thereby support the brake tangential force F2 (that is, a so called pull anchor structure is established). Here, since the engagement portion between the through hole 14b and pad pin 9b is situated more inward in the radial direction than the action line of the brake tangential force F2, in backward-run braking, to the pad 11a, there is applied the moment M2 based on the brake tangential force F2 to rotate the pad 11a clockwise.
Thus, in the disk brake apparatus of the conventional structure, the direction of the moment acting on the pad 11a (11b) in the forward-run braking and the direction of the moment acting on the pad 11a (11b) in the backward-run braking are opposite. Therefore, when the forward-run braking and backward-run braking are repeated, for example, in entering a vehicle into a garage in a parking lot, the attitude or rotation of the pad 11a (11b) is changed greatly counterclockwise and clockwise. Therefore, the attitude of the pad 11a (11b) becomes unstable, whereby abnormal sounds called brake squeals are easy to occur and clonk sounds (click sounds) are also easy to occur.
Here, the prior art technology document relating to the invention includes, besides the above-mentioned patent document 1, the patent document 2. The patent document 2 relates to the opposed piston type disk brake apparatus and, specifically, discloses a structure in which a pair of pad pins respectively provided on the circumferential-direction two end portions of a support are used to support a pad movably in the axial direction. However, this structure also raises a similar problem to the structure of the patent document 1.
[Patent Document 1] JP 2006-520449 A
[Patent Document 2] JP 2007-528468 A